228 
Wigglesworth . — The young Sporophytes of 
to the ingrowth of the thickened part of the wall 1 (PI. XXII, Fig. 17), these 
are surrounded by elongated parenchymatous cells with large nuclei, which 
connect up with the ring of parenchyma which surrounds the main stele and 
which appears to be of the nature of phloem, although true sieve-tubes have 
not been made out in the leaf-trace. Russow 2 states that the leaf- trace 
in Lycopodium consists of a few spiral and reticulate cells, which are 
surrounded by companion cells and a few protophloem elements. In the 
young sporophytes I examined the elements forming the leaf-trace were so 
small that I was unable to distinguish sieve-plates in the elongated cells 
surrounding the xylem. 
When the leaf-trace has passed beyond the endodermis it can be seen 
that the number of elements surrounding the xylem has increased, and that 
some of the walls of the 4 phloem 5 cells have become thickened, so that it is 
difficult to distinguish between the xylem and the remaining elements in 
transverse sections, as the walls of the xylem elements contain little or no 
lignin. The increase in the number of elements forming the leaf-trace 
is not peculiar to this species. It is well marked in L. Phlegmaria , which 
possesses very large leaf-traces, and here it can be clearly seen that the 
leaf-trace is surrounded by a protective sheath of cells resembling those 
surrounding the central cylinder of the stem, and that they have divided 
by walls parallel to the periphery of the bundle. 
Bower 3 found that, amongst the species of Lycopodium he examined, 
the leaf-trace of Z. Phlegmaria most resembled that of Lepidostrobus 
Brownii, both with regard to the small amount of tissue referable to phloem 
and the division of the outer cells by walls parallel with the limits of the 
bundle. Tmesipteris also shows a resemblance in these respects. The leaf- 
trace of Lepidostrobus Brownii is, however, collateral, and in recent 
Lycopods it appears to be concentric. 
(c) Comparison of the stem of the young sporophyte with that of the mature 
plant. Comparing the structure of the stem of the young sporophyte of Z. 
complanatum with that of the mature plant, it will be seen that the stele in the 
upper part of the branches of the latter closely resembles that of the upper 
part of the young sporophyte in there being 3-5 protoxylem groups radially 
arranged and connected by metaxylem in the centre, with usually one or 
more groups separated off from the rest and surrounded by a layer of 
parenchyma. The chief differences lie in the irregular and rapidly changing 
arrangement of xylem and phloem in the basal portion of the stem of the 
young sporophyte, and in the shape of the stem —that of the young 
1 De Bary describes somewhat similar tracheides, which he calls ‘trachae trabeculatae/ as occurring 
at the corners of the vascular bundle of the stems of stronger species of Lycopodium , and in the 
margin of the vascular bundles of the leaves of Juniperus . Compar. Anatomy of Phanerogams and 
Ferns, pp. 163, 164, Fig. 62. 
2 Russow, Mem. de l’Acad^mie Imperiale des Sc. de St-Petersbourg, 7 e Ser., vol. xix. 
3 Bower, On Structure of Lepidostrobus Broivuii. Ann. of Botany, vii, 1893, p. 340. 
